Cufflinks by Josef Koppmann Features Primary Material : 24ct gold and sterling silver Other Materials : pyrite and slate Fitting Type : hinged bar Dimensions (mm) : 14x14x4 One of a Kind : Yes Metal : 24ct gold and sterling silver Gems : pyrite and slate Hallmarked : Yes Cleaning InstructionsThe cufflinks are best kept clean by rubbing and brushing them gently under running water with bicarbonate of soda. Do not submerge in water for long periods and do not clean the cufflinks in ultrasonic cleaning systems.